Natural Lake Foam

Many property owners on Lake Margrethe have become concerned about foam appearing on the lake and shoreline; however, most of the foam observed on lakes and streams is a natural product of nature and is not necessarily an indicator of pollution. Small trout streams, for example, often have naturally occurring pools of foam where fish will hide. The foaming of surface waters on lakes and streams is not a new phenomenon. It is a natural process that has been going on for a long time.

Foam is created when the surface tension of the water (the attraction of surface molecules for each other) is reduced and the air is mixed in, forming bubbles. All lakes contain organic matter, such as algae and plants, and when they decompose, they release cellular products or surfactants into the water, which lessens surface tension. When the wind blows, the waves on the lake agitate this surface agent, transforming it into a sudsy,white foam.

In the late 1950’s and early 1960’s, many communities experienced tremendous foam problems in lakes, rivers, sewage treatment plants, and even in drinking water from contaminated wells. This foam was caused by synthetic laundry detergents that were highly resistant to chemical breakdown and were only slowly degradable when broken down by bacteria. Now, in 2011, the law requires that the sudsing agent of all detergents on the market must be biodegradable, which means that detergents must quickly loose their ability to cause foaming and are unable to produce the long-lasting foam which had been found along many lake’s shores. This detergent foam will have a noticeable perfume smell and is usually whiter in appearance

Natural lake foam will frequently form parallel streaks in open water, caused by wind- induced surface currents. Foam will also collect in large quantities on windward shores, in coves and eddies. This natural foam will have a somewhat earthy, fishy aroma and will have an off-white, tan, or brown coloration. This natural foam can be frequently observed on Lake Margrethe in open water and on windward shorelines.

*The information in this article comes from the New Hampshire Department of Environmental Services